In recent years, it has been reported that the strong toxicity of heavy metal-containing compounds and the accumulation of these heavy metals in the internal organs cause various fatal diseases. For this reason, the use of heavy metals has been strictly restricted.
Trace heavy metals contained in cosmetic products are those released from raw materials used for the production of the cosmetic products, and are problematic when they are present in trace amounts that do not harm human health. However, if cosmetic products contain excessive amounts of heavy metals such as lead, arsenic, antimony, cadmium, mercury, cobalt and nickel, these heavy metals can cause serious diseases such as skin diseases.
The allowable contents of lead, arsenic, mercury, antimony and cadmium in cosmetic products have been restricted, but there are no particular restrictions on other heavy metals. However, the incidence of allergy by heavy metals such as nickel and cobalt has gradually increased, and thus the use of these heavy metals has been gradually limited.
Magnesium, copper, iron and zinc were approved for use in cosmetic products, because they ensure safety for human use depending on their oxidation state or molecular structure. However, the use of such heavy metals in orally inhalable products has been restricted.
Due to the reports of studies on allergy caused by heavy metals and heavy metal toxicity as described above, consumers demand safer products, and thus there is an urgent needed to ensure the safety of cosmetic products against heavy metals.
However, as is known in the analysis field, it is difficult to analyze heavy metals dissolved in complex matrices such as cosmetic products. Analysis instruments that have conventionally been used include atomic absorption spectrometers (AAS) and inductively coupled plasma (ICP) analyzers. However, methods employing these analysis instruments require a long pretreatment time and use strong acids such as hydrofluoric acid, and for this reason, these methods are unsuitable for use in the quality control of raw materials and products, and thus the use thereof is limited.
Patents related to the X-ray fluorescence (XRF) analysis of heavy metals have already been reported. However, these patents mention neither technology relating to the preparation of standard samples nor technology relating to matrix correction methods. Thus, when the technologies disclosed in these patents were applied to complex matrices containing organic materials and various inorganic metals, such as cosmetic products, accurate analysis was difficult and trace quantitative analysis was impossible, due to errors caused by matrix differences and measurement errors caused by interference.